This invention relates to a mechanism for attaching a trough to a vibratory feeder of the kind principally used for a combinational weighing machine for supplying articles to weigh hoppers for weighing.
Vibratory feeders such as electromagnetic feeders have been in use, for example, for a combinational weighing machine adapted to supply articles to be weighed to many weigh hoppers for weighing, to select a combination of a plurality of such weigh hoppers that will provide a total weight which may be the closest to a target weight, to cause the articles to be discharged from these selected weigh hoppers, and to obtain products by packaging those discharged articles at a later stage. Electromagnetic feeders have been in use for supplying the articles to be weighed to the weigh hoppers.
An electromagnetic feeder is typically comprised of a trough-supporting base which is supported by a plate spring and is adapted to be vibrated and a trough which is affixed to this base and serves to receive articles (to be weighed) at a backward section and to transport them in a forward direction by a resonance phenomenon as the trough is vibrated by an electromagnetic mechanism. Japanese Utility Model Application Jikkai 62-96009 disclosed a trough-attaching mechanism for such an electromagnetic feeder characterized wherein a trough and a trough-supporting base are removably attached to each other by screws. With a trough-attaching mechanism of this kind, however, screws become loose after a use over a long period of time. In view of the above, the present applicant proposed, in Japanese Utility Model Publication Jikko 62-2508, a new trough-attaching mechanism which does not cause the screws to become loose.
As shown in FIG. 8, this mechanism is characterized as having a trough-supporting base 50 supporting at a forward position and a backward position on its upper surface a front positioning member 51 having a downwardly facing inclined surface and a back positioning member 52 having an upwardly facing inclined surface, respectively. A front contact member 55 and a back contact member 56 each having a slope contacting the inclined surface of the aforementioned front and back positioning members 51 and 52, respectively, are affixed to a bottom plate 54 of a trough 53. Mutually corresponding pairs of positioning members 51 and 52 and contact members 55 and 56 are pressed against each other across their inclined surfaces so as to properly position the trough 53 with respect to the base 50. The trough 53 is fastened to the base 50 by means of a clamping mechanism 57 comprising a toggle means at a backward position of the base 50 such that the bottom plate 54 of the trough 53 is pressed downward and the back positioning member 52 and the back contact member 56 are strongly compressed against each other.
This mechanism has the advantage of providing a high vibration-transmitting efficiency to the trough 53. If the slope .theta..sub.1 of the inclined surface is made small, however, it becomes necessary to slide the trough 53 at a small angle against the base 50 in order to assemble them together. Since the assembly work will be difficult to perform in such a situation, the slope .theta..sub.1 must be made larger than the angle of propagation of vibrations (usually 20.degree. from the horizontal). As a result, the upwardly directed component of the force of the vibratory acceleration comes to act significantly on the clamping mechanism 57. In the case of a large feeder with the front and back positioning members separated by a large distance, in particular, the inclined surfaces vibrate so as to hit against each other and to separate from each other (that is, they vibrate relative to each other) due to the bending of the trough 53 itself unless the rigidity of the trough 53 is extremely high, and there is a large noise produced and propagated to the environment.
The present invention has been accomplished in order to eliminate these problems, and it is an object of the invention to provide an improved trough-attaching mechanism capable of securely fastening a trough to a trough-supporting base without causing noise to be generated due to relative vibrations between them.